Fuel injector

ABSTRACT

A fuel injector for an internal combustion engine, comprising an injector body and a plunger reciprocable in said body. An injection chamber in the body receives fuel from a fuel supply, and the plunger is moved in an injection stroke to force fuel from the injection chamber and out of the injector through spray holes in the injector body. A valve in a flow passage between the chamber and the spray holes is normally open to permit fuel flow during injection. The plunger moves the valve toward its closed or seated position during the injection stroke, and when the valve closely approaches the seated position, a hydraulic force develops which forces the valve to its seat and thereby abruptly terminates injection. Release of fuel pressure after termination of injection is attained by opening a spill port, the flow passage for the spilled fuel being restricted in order to obtain a gradual release of the fuel pressure in the chamber. The resulting gradual release of fuel pressure in the chamber holds the valve firmly seated and thus prevents secondary injection.

United States Patent [191 Perr et a1. Aug. 27, 1974 [5 FUEL INJECTOR 548,454 10/1942 Great Britain 239/89 [75] Inventors: Julius Pm; George L. Mumean, 447,324 4/1949 Italy 239/89 both of Columbus, Ind.

[73] Assignee: Cummins Engine Company, Inc., Columbus, Ind.

[22] Filed: Jan. I5, 1973 [2]] Appl. No.: 323,624

[52] US. Cl 239/89, 239/90, 239/95 [51] Int. Cl. F02m 47/02, F02m 45/ 1O [58] Field of Search; 239/88-91, 239/5, 96, 95

[56] References Cited UNITED STATES PATENTS 1,901,723 3/1933 Belyavin 239/89 2,872,247 2/1959 Shallenberg 239/89 2,898,051 8/1959 Teichert 239/88 X 3,104,817 9/1963 Vander Zee et al....; 239/90 3,257,078 6/1966 Mekkes 239/90 3,351,288 11/1967 Perr 239/89 3,409,225 11/1968 Maddalozzo et a1 239/89 3,486,696 12/1969 Dreisin 239/89 3,737,100 6/1973 Dreisin 239/89 FOREIGN PATENTS OR APPLICATIONS 582,783 ll/1946 Great Britain 239/89 Primary Examiner-Robert S. Ward, Jr. Attorney, Agent, or Firm-Hibben, Noyes & Bicknell 5 7 ABSTRACT A fuel injector for an internal combustion engine, comprising an injector body and a plunger reciprocable in said body. An injection chamber in the body receives fuel from a fuel supply, and the plunger is moved in an injection stroke to force fuel from the injection chamber and out of the injector through spray holes in the injector body. A valve in a flow passage between the chamber and the spray holes is normally open to permit fuel flow during injection. The plunger moves the valve toward its closed or seated position during the injection stroke, and when the valve closely approaches the seated position, a hydraulic force develops which forces the valve to its seat and thereby abruptly terminates injection. Release of fuel pressure after termination of injection is attained by opening a spill port, the flow passage for the spilled fuel being a restricted in order to obtain a gradual release of the fuel pressure in the chamber. The resulting gradual release of fuel pressure in the chamber holds the valve firmly seated and thus prevents secondary injection.

. 35 Claims, 24 Drawing Figures mmww zww ai.a31.s4 s

VARIABLE 3 PRESSURE FUEL -2 SUPPLY SHEH 6 BF 8 PATENTS] 13271974 FUEL INJECTOR One type of fuel injector for an internal combustion engine is referred to as a unit injector and includes, as a unitary structure, a fuel pump and a fuel injection nozzle. The injector is mounted with the nozzle projecting into an engine cylinder, and in the operation of such an injector, the pump, consisting of a cam actuated plunger, forces a quantity of fuel from the nozzle under high pressure, thereby atomizing the fuel, into an engine cylinder at the proper time in the engine cycle.

To attain greater efficiency in burning fuel in the cyl' inders of either a four cycle or a two cycle engine and to reduce the amount of pollutants emitted by such engines, it is important that the fuelbe injected at an optimum rate and that the injection of fuel into the cylinders be terminated as abruptly as possible. The reason for this will become apparent from the following discussion of a four cycle engine, although the general principles also apply to two cycle engines. In a four cycle combustion ignition engine, fresh air is drawn into an engine cylinder during the intake stroke of the piston, at which time the piston is moving away from top-dead-center (TDC). l During the compression stroke, the air intake-passage is closed and the movement of the piston toward TDC compresses, andthus heats the air in the cylinder. Injection of fuel may start at, for example, approximately 35 before TDC and the fuel ignites at approximately before TDC. There then follows a period of 7 controlled burning during which the fuel is burned as it is injected. There is mixing of fuel and the air because the fuel is being injected under high pressure, this pressure preferably being adjusted to cause the atomized fuel to be forced outwardly, close to, but not in contact with, the outer periphery of the cylinder. The fuel flow rate is preferably at 'a value chosen to achieve good combustion. 7

During the latter part of the injection period, the pressure on the fuel being injected starts to drop and in conventional injectors the pressure drops gradually until injection ceases. When the injection pressure drops below a certain value, combustion is inefficient because the fuel is not forced sufficiently far out in the cylinder to become thoroughly mixed with the air. Further, many injectors permit secondary injection, which is leakage of fuel from the injector after injection should have been stopped. Such secondary injection is due to fuel trapped unde high pressure near the bottom of the injector valve, such pressure forcing the valve back open after the valve has been closed by the cam. Consequently, there is an amount of unburned and partially burned fuel remaining in the cylinder at the start of the exhaust stroke, which is due both to the above mentioned secondary injection and to inefficient combustion, and it is this fuel which accounts for a large part of the visible smoke and toxic unburned hydrocarbons emitted by the engine. It will therefore be apparent that the amount of harmful emissions would be reduced if the fuel injection were abruptly terminated at the point when combustion becomes inefficient.

J.P. Perr US. Pat. No. 3,351,288 discloses a prior art unit injector wherein the lower end of a plunger seats in order to end injection, and wherein, during operation, the pressure on the fuel being forced from the injector gradually drops near the end of an injection period. It might be possible to obtain a more abrupt end of-injection with such an injector by designing the cam which drives the injector with a steeper ramp and thus forcing the plungers lower end hard against the nozzle. Such a construction would, however, quickly result in failure of the parts because the stress on the cam and follower surfaces, during injection, would be excessive and because the momentum of the entire plunger and actuating linkage against the nozzle would eventually damage the latter. In addition, hydraulic pressure within the injection after the plunger seats tends to lift the plunger off its seat, and thus there is a tendency for secondary injection to occur.

The prior art also includes a unit injector wherein an injector needle part is carried by a plunger and is moved by a spring to a seated position to terminate injection. The needle part seats on a thin-walled part of the injector body and the use of a spring to seat the nee dle part thus protects the injector from the strain of high mechanical impact. The plunger is seated in a heavily supported part of the injector body to support the strain of mechanical impact, but such seating limits the amount of overrun permitted of the plunger, Limited overrun is disadvantageous as will be apparent hereinafter.

It is therefore an object of the present invention to provide an injector wherein the injection of fuel may be abruptly terminated without damage to the injector or other engine parts, and wherein secondary injection cannot occur. In accordance with the present invention there is provided a fuel injector for an internal combustion engine, comprising an injector body having a plunger bore and a fuel receiving chamber formed therein, said body further including spray holes formed in one end thereof and a passage connecting said chamber with said spray holes, a plunger reciprocably mounted in said bore and adapted. to exert pressure on fuel in said chamber when moved toward said one end, a valve member movably mounted in said passage and movable to a seated position where it closes said spray holes, said valve member normally being in a retracted position where said spray holes are open, said valve member moving to said seated position in response to movement of said plunger toward said one end, and pressure release means for relieving pressure in said chamber at the time that said valve member moves to said seated position.

. The valve member is separate from the plunger and is moved toward its seated position by the movement of the plunger until the valve member is close to its seat, at which time a pressure drop develops adjacent the seat causing the valve member quickly to move to its seated position. In a preferred form of the invention, the pressure drop pulls the valve member away from the plunger and into its seated position. Thus, an abrupt end of injection is obtained without a high mechanical force being exerted on the valve member or the other injector parts. Further, the hydraulic force is in a direction to hold the valve, member in its seated position, thus preventing secondary injection. I

In addition to the foregoing advantages, an injector in accordance with the invention is advantageous in that up to the point of termination of injection, the rate of injection is very high, thus producing good combustion. The pressure on the fuel in the injection chamber at the end of injection is gradually relieved thereby holding the valve member seated and protecting the injector parts from the strain of high mechanical impact.

Further, at the beginning of the injection stroke there is a relatively large volume of fuel in the chamber and consequently a relatively slow build-up in pressure resulting in a good injection rate.

This invention may be better understood from the following detailed description taken in conjunction with the accompanying figures of the drawings, wherein:

FIG. 1 is a fragmentary view partially in section of an engine including an injector embodying the invention;

FIG. 2 is an enlarged longitudinal sectional view of one form of the injector;

FIGS. 3 to 5 are fragmentary views of a portion of the injector shown in FIG. 2 but showing different operating positions of the injector'parts;

FIG. 6 is a fragmentary sectional view of another portion of the injector shown in FIG. 2;

FIG. 7 is a sectional view taken on the line 7-7 of FIG. 2;

FIGS. 8 and 9 are curves illustrating the operation of the injector;

FIGS. 10 to 12 are views showing an alternate form of injector;

FIG. 13 is a view showing another alternate form of injector;

FIGS. 14 and 15 are views showing still another alternate form of injector;

FIG. 16 is a view showing still another alternate form of injector;

FIGS. 17 to 20 are views showing still another alternate form of injector;

FIGS. 21 and 22 are views showing still another alternate form of injector;

FIG. 23 is a view showing still another alternate form of injector; and

FIG. 24 is a view showing still another alternate form of injector.

The engine partially shown in FIG. 1 includes a cylinder head 51 and a block 52. A cylinder liner 53 is mounted in the block in a conventional manner and forms a cylinder 55. A piston 56 is mounted for reciprocating movement within the cylinder 55, and the upper end of a connecting rod 57 is pivotally connected to the piston 56 by a wrist pin 58. Piston rings 59 are mounted on the piston 56 and form a seal between the piston 56 and the liner 53. The crown 61 of the piston 56 has an annular cavity 62 formed in its upper surface.

The head 51 of the engine includes coolant passages 63 therein, and intake and exhaust valve mechanisms (not shown) connect the upper end of the cylinder 55 with intake and exhaust manifolds (not shown) of the engine. A fuel injector 64 embodying the invention is mounted in the head 51 with its lower end 66 extending through an opening 67 formed in the head 51, the end 66 opening into the interior of the cylinder 55 at the center thereof. The injector 64 is mounted in an open ing 68 formed in the head 51 and is held in place by a yoke-shaped clamp 69. The clamp 69 has two fingers 71 which press down against the upper surface of a flange 72 of the injector 54, and a screw 73 holds the fingers 71 firmly against the injector flange 72. The screw 73 extends through a hole 74 in the clamp 69 and is threaded into the head 51.

The injector 64 is operated by a connecting linkage mechanism 75 including an injector cam 76 which is fastened to and rotates with an engine driven cam shaft 77. A cam follower mechanism 78 includes a roller 79 which rides on the outer surface of the rotating cam 76. The cam follower mechanism 78 further includes a tappet 81 for the roller 79, the tappet 81 being reciprocably mounted in an opening 82 of the block 52.

Connected to the cam follower mechanism 78 is a push rod 87 which extends upwardly to a rocket arm 88 pivotably mounted on the head 51 by a rocket shaft 89. A pivotable arrangement including an adjusting screw 91 connects the upper end of the push rod 87 with one end of the rocker arm 88. The other end of the rocker arm 88 pivotably engages the upper rounded end of a link rod 93 which extends downwardly to operate the injector 64.

As will be explained in greater detail hereinafter, the injector 64 includes a fuel intake or supply passage and fuel drain or return passages therein. Fuel is supplied to and returned from the injector 64 by fuel passages or rails formed in the head 51. The fuel supply rail is shown schematically in FIG. 1 and is indicated by the reference numeral 96 and receives fuel from, in the present illustration, a variable pressure fuel supply 97. Thefuel return rail is also indicated schematically and is indicated by the reference numeral 98 andcarries fuel from the injector 64 to a sump, which may be the main fuel tank. The arrangement of the fuel supply and return rails and the construction of the fuel supply 97 do not form part of the present invention.

With reference to FIGS. 2 to 7, the injector 64 includes a body including an adaptor 101, a barrel 102 which abuts the lower end of the adapter 101, and a cup or nozzle which abuts the lower end of the barrel 102. The nozzle 105 forms the lower end 66 of the injector, referred to in connection with FIG. 1. The foregoing parts 101,102 and 105 are held in assembled relation by a retainer 103 which fits around the barrel 102 and has its upper end internally threaded as at 104 to the lower end of the adapter 101. The lower end of the retainer 103 includes a ledge 106 which engages and presses upwardly against a shoulder 107 formed on the outer periphery of the nozzle 105. Thus, when the retainer 103 is threaded tightly on the adapter 101,'the' ledge 106 presses upwardly against the nozzle 105, and thereby holds the parts tightly assembled. Vertically extending pins (not shown) may be provided to angularly align the adapter 101 and the barrel 102.

At the upper end of the adapter 101 is secured an adapter extension 111 having the flange 72 formed thereon, which is engaged by the clamp 69. The interior of the extension 111 is internally threaded and a stop screw 112 is threaded into the extension 111.. A lock nut is preferably provided on the stop screw 1 12 to lock the stop screw 112 in an adjusted position. The opening 67 in the head 51 includes a seat 116 which abuts the lower end of the injector 64 to form a seal. Thus, the U-shaped yoke-clamp 69 presses downwardly against the flange 72 and holds the injector pressed tightly against the seat 116, thereby clamping the injector 64 firmly in place in the head 51.

The fuel supply rail 96 communicates with an annular groove 120 in the outer periphery of the retainer 101, and the fuel return rail 98 communicates with a second annular groove 121 formed in the retainer 101. O-ring seals 122 are positioned in groovesformed in the retainer 101 above, below and between the grooves 120 and 121, to seal the grooves.

A plunger bore 126 is formed centrally in the adapter 101 and in the barrel 102, and a plunger 127 is mounted for reciprocating movement in the plunger bore 126. A flange 128 formed on the upper end of the plunger 127 extends over the upper surface of a stop washer 129. A retraction spring 131 is positioned between the stop washer 129 and a ledge 132 formed on the inner periphery of the adapter 101, the compression spring 131 urging the stop washer 129 upwardly toward the screw 112. The outer periphery of the stop washer 129 extends into a vertical spaced formed between the upper end of the adapter 101 and the stop screw 112. During installation of the injector in the engine, a technician tightens the screw 91 to properly tension the cam actuated mechanism 75, and if the screw 91 is excessively tightened, the washer 129 engages the retainer 101 and thus prevents damage to the injector tip. The washer 129 and the retainer 101 do not however normally meet.

The plunger 127 is formed in two parts, an upper hollow coupling part and a lower part which is secured to the coupling part. Thelink 93 extends through the coupling part and pivotally engages the upper end of the lower part. During turning movement of the cam 76, the link 93 moves downwardly and overcomes the force of the spring 131 in order to move the plunger 127 downwardly. This action ejects fuel from the injector and into the engine cylinder 55 as will be explained subsequently. The spring 131 returns the plunger 127 t to its upward. position upon continued turning movement of the cam 76.

Below the lower end of the plunger 127 and within the nozzle 105 is mounted an elongated tip valve 141 (FIGS. 2 to 5 and 7). In the present instance, the tip valve 141 is generally cylindrical and the nozzle 105 has a cylindrical bore 142 formed therein, the tip valve 141 being mounted for reciprocating movement within the bore 142. The lower end of the bore 142 is slanted inwardly to form a conical valve seat 143, and the lower end of the tip valve 141 has a complementary shaped valve portion 144 which, when seated on the seat 143, seals the lower end of the bore 142. The lower end of the nozzle 105 has spray holes 146 and a sac hole 147 formed therein, through which the fuel passes as it is injected into the interior of the cylinder 55.

The bore 142 has an enlarged diameter upper portion 136 (FIG. 5) which receives a spring 156 to be described. The lower end of the bore 142 is stepped radially inwardly as at 137 to the conical valve seat 143. The tip valve 141 has a close sliding fit in the intermediate portion of the bore 142, and it is also stepped radially inwardly as at 138 to a smaller diameter portion 145 which is equal in diameter to the upper end of the valve portion 144. As shown in FIGS. 2 and 3, when the tip valve 141 moves downwardly to seat the portion 144 on the valve seat 143, the steps 137 and 138 are axially spaced a short distance apart.

The upper end of the tip valve 141 has an internally threaded hole indicated at 148 (see FIG. 2), and a screw 149, preferably of the Lock Tite type, is screwed into the threaded hole 148. An impact button 151 is positioned around the head 153 of the screw 147, the button 151 having an inwardly extending flange 152 which fits underneath the head 153 of the screw 149. The button 151 extends upwardly around the outside of the head 153 and normally engages the lower end surface of the plunger 127, as shown in FIGS. 3 to 5.

The lower end of the plunger 127 may be hollowed as indicated at 155 to provide clearance for the head 153. The button 151 is forced upwardly toward the plunger 127 by the outer compression spring 156 which has its upper end in engagement with the underside of the button 151 and its lower endseated on a shim 157 which is supported on a ledge in the nozzle 105. Further, the tip valve 141 is urged downwardly relative to the but ton 151 by an inner compression :spring 158 whichextends between the underside of the button 151 and the upper surface of the tip valve 141. The two springs 156 and 158 are of course arranged concentrically around the screw 149 and within the bore 142.

As previously mentioned, fuel flows to'the injector 64 through the passage 96 formed in the head 51, the fuel being received from the variable pressure fuel supply 97. The adapter 101 has a fluid passage 165 formed therein which opens from the groove 120. A filter screen 166 covers the opening of the supply passage 165, and a balance orifice 167 is formed in a plug located in the opening of the supply passage 165. The passage 165 connects with a passage 168 (FIGS. 2 and 6) formed in the barrel 102, and a check valve 169 is located in the passage 168. The foregoing passages and check valve are generally similar to those shown in the previously mentioned Perr US. No. 3,351, 288. The lower end of the passage 168 communicates with an annular groove 171 (FIGS. 2 and 6) formed in the upper surface of the nozzle 105. Angularly displaced from the passage 168 is a passage 172 (FIGS. 2 to 5) in the barrel 102, which extends upwardly from the groove 171. A feed or metering orifice 173 connects the passage 172 with the plunger bore 126 and a scavenging port or orifice 174 is located above or upstream from the orifice 173 and also connects the passage 172 with the plunger bore 126.

The return rail 98 leads from the groove 121 of the injector 64, as previously explained, and two return or drain passages 176 and 177 (FIG. 2) are formed in the adapter 101 and in the barrel 102. The two passages 176 and 177 are angularly displaced, and the upper ends of both passages 176 and 177 open into the groove 121, while the lower ends of both passages open into the plunger bore 126. The lower end of the passage 176 is referred to herein as a spill port and is indicated by the reference numeral 178. The lower end of the passage 177 is referred to herein as the drain port and is indicated by the reference numeral 179. The scavenging port 174 and the drain port 179 are substantially transversely aligned, and the plunger 127 has an annular recess or groove 181 formed therein, which is located to connect the ports 174 and 179 when the plunger 127 is in its extended or downwardly displaced position, shown in FIGS. 2 and 3. The orifice 173 is located below the ports 174 and 179 and is positioned such that it is uncovered by the lower end of the plunger 127 only when the plunger is in its retracted or upwardly displaced position, shown in FIG. 4. The spill port 178 is formed below the port 179 and is located relative to a second annular groove 182 in the plunger 127 such that the groove 182 opens the spill port 178 to a limited extent only when the plunger 127 is in its.

maximum extended position, shown in FIG. 3. As best shown in FIGS. 2 and 4, a hole 183 extends axially through the screw 149 and from the upper end of the tip valve 141 downwardly to the valve portion 144. A radially extending hole 184 (FIGS. 2 and 7) is formed in the tip valve 141 below the step 138 and above the valve portion 144, from the exterior surface of the tip valve 141 to the center hole 183. The upper end of the hole 183, at the top of the screw 149, opens into the cavity or recess 155 formed in the lower end of the plunger 127. An axial hole 186 (FIG. 3) is formed in the lower end of the plunger 127 and extends from the cavity 155 to the level of the groove 182, and a radial hole 185 connects the hole 186 with the groove 182. Consequently, as shown in FIG. 3, when the plunger 127 is in its maximum downwardly extended position, the holes and passages 183 to 186 place the portion of the bore 142 around the lower end of the tip valve 141, in communication with the spill port 178. I

A number of the passages in the barrel 102 are formed by drilling holes from the outside of the barrel, and in a number of instances, the outer ends of the holes are sealed by plugs 190 (FIG. 3).

The injector further includes fuel passage means connecting the upper and lower portions of the bore 142. In the form of the injector shown in FIGS. 1 to 7, this passage means is formed in the tip valve 141. With particular reference to FIGS. 5 and 7, a plurality of longitudinally extending slots or grooves 189 are formed in the outer surface of the tip valve 141, the grooves 189 extending from its upper end downwardly to the step 138. The total cross-sectional area of the grooves 189 must be greater than the total area of the spray holes 146 to prevent a hydraulic lock from occurring during injection of fuel.

Considering the operation of the injector disclosed in FIGS. 1 to 7, when the cam shaft 77 (FIG. 1) is at an angular position such that the follower roller 79 en-. gages a reduced radius section 191 of the cam 76, the plunger 127 is in its maximum upwardly displaced, or retracted, position which is shown in FIG. 4. As previously mentioned, the spring 131 moves the plunger 127 to this position, and the spring 156 moves the tip valve 141 upwardly and holds the button 151 against the plunger 127. FIG. 8 shows a curve 192 representing the plunger 127 travel as a function of the angle of the crankshaft driven by the piston 56. The plunger 127 is in its maximum retracted position (FIG. 4) during the portion 193 of the curve 192, this retracted position occurring from approximately the end of the air suction strokeuntil approximately 50 before the end of the compression stroke of the piston 56. During the time that the plunger 127 is in the retracted position, fuel flows from the supply 97, through the passages 165, 168 and 172, through the metering orifice 173 and into an injection or metering chamber 194 (FIG. 4). The chamber 194 is formed by the space below the plunger 127 within the bore 142 of 'the nozzle 105 and, when the plunger 127 is retracted, within the lower end of the plunger bore 126. The tip valve 141, the springs 156 and 158, the bolt 149 and the button 153 are located in the injection chamber 194. While the plunger 127 is retracted, the land portion of theplunger 127 between the grooves 181 and 182 closes the scavenging port 174 and thus prevents flow of fuel between the ports 174 and 179. The portion of the plunger 127 below the lower groove 182 closes the spill port 178. The quantity of fuel flowing into the injection chamber 194 is dependent upon the pressure of the fuel from the supply 97, the size or flow area of the metering orifice 173, and the length of time the plunger 127 is retracted and the metering, orifice is open. Since the amount of fuel injected into the cylinder 55 in each cycle is dependent upon the quantity of fuel metered into the injection chamber 194, the amount of fuel injected into the cylinder 55 in each engine cycle may thus be varied by a change in the fuel pressure.

Continued turning movement of the cam shaft 77 in the counter-clockwise direction as seen in FIG. 1 causes a ramp 196 of the cam 76 to engage the roller 79 and displace it upwardly and the plunger 127 downwardly toward the fuel in the injection chamber. The chamber 194 is always only partially filled with fuel when the plunger starts downwardly on its injection stroke, and injection starts when the lower end of the plunger meets the fuel and causes pressure to build up in the fuel in the metering chamber 194. The plunger 127 meets the fuel at approximately the point 193a on the curve 192. Shortly after the lower edge of the plunger 127 closes the orifice 173, the lower edge of the groove 181 of the plunger 127 opens the two ports 174 and 179 (FIG. 5), permitting scavenging fuel to.

flow through the passage 172, through the ports 174 and 179 and the groove 181, to the drain passage 177.

The rate at which the pressure builds up in the injection chamber is gradual because of the large volume, as compared with conventional injectors, of fuel trapped in the injection chamber 194, and this gradual pressure build-up is highly advantageous because it produces a gradual increase in the rate of fuel injection. This gradual rate increase is illustrated by the curve of FIG. 9, and produces good fuel burning characteristics The movement of the plunger 127 from the position shown in FIG. 5 toward the position shown in FIG. 2 creates extremely high fuel pressure in the injection chamber 194. The fuel in the chamber 194 flows downwardly through the slots 189 formed in the tip valve 141, to the space below the step 138, to the sac hole 147, and out of the spray holes 146. As previously mentioned, the total area of the slots 189 must be much greater than the total area of the spray holes 146 to prevent the formation of a hydraulic lock. This fuel is sprayed into the cylinder 55 in highly atomized form, from the holes 146 which are regularly spaced around the circumference of the nozzle 155, resulting in uniform distribution of the atomized fuel in the cylinder 55. Fuel injection starts at approximately the point indicated by the reference numeral 193a (FIG. 8) which point is dependent upon the quantity of fuel metered into the chamber 194. With reference to FIG. 9 which represents fuel flow rate as a function of time, it will be noted that the fuel flow rate increases as the plunger 127 is forced downwardly and reaches its maximum rate at the point indicated by the numeral 203.

As the plunger 127 moves downwardly and displaces fuel from the chamber 194, the tip valve 141 is also moved downwardly by the force of the plunger 127 on the impact button 151, the inner spring 158 holding the valve 141 extended downwardly from the button 151. When the plunger almost reaches the position shown in FIG. 2, the size of the flow area between the tip valve portion 144 and the seat 143, becomes less than the flow area of the spray holes 146. At this point, the pressure in the sac hole 147 quickly drops clue to the throttling of the fuel flow between the portion 144 and the seat 143, and this same throttling causes a rapid increase in the fuel pressure above or upstream of the portion 144. This rapid change in fuel pressures creates a downwardly directed hydraulic force on the tip valve 141, which overcomes the force of the spring 156 and moves the valve 141 downwardly increasingly faster than the plunger 127. As shown in FIG. 2, the hydraulic force moves the impact button 151 and the tip valve downwardly out of engagement with the plunger 127 and moves the tip valve 141 into engagement with the seat 143. With reference to FIG. 8, the line 1931b represents the travel of the tip valve 141 and it will be noted that thetip valve moves abruptly to the position of the seat 143 indicated by the numeral 193C in FIG. 8. Thus, the tip valve 141 abruptly terminates injection while the plunger 127 is still moving downwardly, and, because of the small size of the tip valve, injection is terminated with very little mechanical impact on the thin walled portion of the cup 105 in which the sac hole 147 is located. The spill port 178 is just starting to open when the tip valve 141 seats, and the restricted opening plus the continued downward movement of the plunger 127 results in the maintenance of a hydraulic force on the upper end of the tip valve, which holds the tip valve seated and therefore prevents secondary injection. The hydraulic pressure on the upper end of the tip valve acts over a much larger area and is much higher than the cylinder pressure acting on the lower end of the tip valve, and therefore the tip valve is held firmly seated. Such operation is the opposite of prior art injectors wherein the pressure on the fuel trapped in the injector when the plunger seats, is in the direction to lift the plunger off its seat. Such prior art injectors, consequently, permit secondary injection of fuel, which is not true of the present injector. The valve formed by the portion 144 and the seat 143 is very close to the sac hole 147 and the size of the sac hole is very small. Consequently, there is essentially no fuel which can dribble into the cylinder. The lower end of the plunger then again engages the impact button 151 and the lower edge of the groove 182 increasingly opens the spill port 178 (FIG. 3). Flow out of the chamber 194 continues to be restricted, however, because of the realtively small size of the flow passages, such as the passage 186, and because, as shown in FIG. 3, the spill port 178 is gradually and only partially opened. Therefore, the pressure in the chamber 194 is only gradually released by the opening of the spill port 178, and this continued hydraulic force plus the force of the spring 158 holds the tip valve seated and prevents secondary injection. The plunger 127 and the impact button 151 move downwardly during a period of overtravel, indicated in FIG. 8 by the portion 193d of the curve 192, which is between the line 1930 and a line 1'93e. During this overtravel, fuel is squeezed from the chamber 194 through the passages 184', 189, 186 and 182 to drain, which is advantageous because it removes from the lower end of the injection chamber 194 any air bubbles and extremely small size carbon particles that may collect there. The carbon particles enter the injector through the spray holes 146 when the tip valve 141 is up. The fact that the impact button 151 is pressed tightly against the lower end of the plunger prevents fuel from flowing out of the top of the chamber 194 to the passage 186. Consequently, fuel enters the chamber 194 at its upper end and fuel is drained from the chamber 194 at its lower end, providing fuel flow in a loop through the chamber 194 and clearing it of any air bubbles and the small size carbon particles. The plunger remains in its lower extended position during the remainder of the power stroke and during the exhaust stroke of the piston 56, as scavenging fuel flows from the port 174 through the groove 181, and out of the port 179 to drain.

With reference to FIG. 9, it will be apparent that the fuel flow rate drops extremely abruptly to zero on the portion of the curve indicated by the reference numeral 211, and this is accomplished without excessive load on the tip valve 141 and on the nozzle of the injector.

Since the injection of the fuel is abruptly terminated at approximately the point 212, fuel is not leaked into the cylinder during the portion of the engine cycle when it could cause a large amount of smoke and unburned hydrocarbons, and the effective duration of injection can be reduced. Thus, the amount of visible smoke and other pollutants from the engine is drastically reduced.

As acomparison to more conventional injectors, it should be apparent that, if the tip valve 141 were rigidly attached to the plunger 127, it would have to be forced downwardly very hard against the nozzle 105 in order to close off injection abruptly and such high impact forces on the injector parts would quickly damage it. The dashed line 193f in FIG. 8 illustrates the valve movement in an injector where the valve is rigid with the plunger, as shown in Perr U.S. Pat. No. 3,351,288, for example, and it should be noted that such a valve moves relatively slowly to a seated position. The dashed line 210 in FIG. 9 illustrates the gradual drop in flow rate, which is customary in a conventional injector. The portion of the fuel injected after the point 212' is poorly burned.

The injector thus obtains an abrupt termination of injection at a point in the injection cycle when the rate of injection is very high, which is a highly advantageous feature. This feature is also illustrated by FIG. 8 wherein the slopes of lines 193b, 193a and l93f where they cross the line 193a indicate the degree of abruptness of the termination of injection. The line 193b illustrates the operation of the injector forms of FIGS. 1 through 16, and has a very steep slope, and the line 1933b occurs when the plunger 127 is moving rapidly. Since it is not necessary for the plunger to seat in order to terminate injection or to stop its movement, the plunger is permitted almost unlimited overrun, represented by line 193d. Movement of the plunger and the actuating mechanism is stopped by the retraction spring 131 and by compression and gradual release of the fuel in the injection chamber. The slope of the line 193a where it crosses the line 193a represents the abruptness of termination of injection of the injector forms illustrated in FIGS. 17 to 24, and it will be noted that this slope is also very steep. For comparison, the line 1931f represents the operation of a prior art injector of the character shown in the Pen U.S. Pat. No.

3,351,288, and the slope of this line is quite low.

Applicants injector also differs from prior art injectors in the function of the spill port 178. In applicants injector, opening of the spill port 178 does not terminate injection. Termination of injection is accomplished by seating of the tip valve 141, and opening of the spill port serves to release pressure in the injection chamber in order to protect the parts. In prior art injectors including spill ports, opening of the spill port serves to terminate injection. v

The plunger 127 and the. tip valve 141 are held in the downward position shown in FIG. 3 during the power and exhaust strokes, thereby preventing any cylinder gases from entering the injector through the spray holes. During the suction stroke, the roller 79 moves down a second ramp 196a of the cam 76, permitting the spring 131 to return the plunger 127 upwardly to the position shown in FIG. 4, and the outer spring 156 moves the tip valve 141 upwardly also to start a new cycle.

In an injector of form shown in FIGS. 1 to 7, the pressure in the injection chamber rises to approximately 15,000 psi, while the pressure of the fuel received from the fuel supply is on the order of 200 psi. The total plunger stroke may be approximately 0.2 inch, and the volume of fuel in the injection chamber at the start of injection is approximately times greater than the volume of fuel inthe injector shown in the above mentioned Perr patent.

The form of the injector illustrated in FIGS. 10 through 12 is generally similar in construction and operation to the form shown in FIGS. 1 through 7. This injector comprises a barrel 225, a cup or nozzle 226, and a retainer 227 that holds the cup 226 and barrel 225 in assembled relation with an adapter (not shown). A fuel supply passage 228 is formed in the barrel 225 and leads from a source of fuel under variable pressure to an annular groove 229 formed in the upper surface of the cup 226. A vertically extending supply passage 231 is also formed in the barrel 225 at a location which is angularly displaced from the supply passage 228, and leads upwardly from the groove 229 to a metering orifice 232 and to a scavenging port 233. The orifice 232 and the port 233 open into a plunger bore 235 in which a plunger 238 is reciprocably mounted. The plunger 238 includes a first or upper reduced diameter portion 239 (FIGS. 11 and 12) which is located to connect the port 233 with a drainport 237 when the plunger 238 is in its downwardly displaced position, shown in FIGS. 11 and 12. The plunger also includes a second or lower reduced diameter portion 241 which interconnects a spill port 242 wih a drain port 236 only when the plunger 238 is in its downwardly displaced position which is shown in FIG. 12, the ports 236 and 242 being formed in the barrel 225 at angularly displaced positions. The ports 236 and 237 are connected to two drain passages 240 which are similar to the passages 176 and 177 shown in FIG. 2. The spill port 242 forms part of spill passage 243 formed in the barrel 225 between the bore 235 and an injection chamber 246, the lower end 244 of the passage 243 opening into the injection chamber 246. A spill restriction is provided in the passage 243, the restriction consisting of a plug 247 which is fixed in place in the passage 243 and which has a small orifice 248 formed therein.

The injection chamber 246 is generally similar in configuration to the chamber 194 of the injector form shown in FIGS. 1 through 7, and therefore will not be described in detail. A tip valve 251 is movably mounted in the chamber 246 and includes a lower conically shaped valve portion 252 which, when seated on a conical valve seat 253 of the cup 226, closes a sac hole 260 and spray holes 254 formed in the cup 226. Again, the

tip valve 251 includes fuel passages 250 formed on the washer 259 is positioned around the upper end of the shank 257, and a nut 261 is threaded onto the end 258 over the washer 259. Inner and outer springs 262 and 263 are mounted around the tip valve 251, these two springs being mounted similarly to and performing the same function as the springs 157 and 158 shown in FIGS. 2 to 5. Thus, the outer spring 263 urges the washer 259, the nut 261 and the tip valve 251 upwardly relative to the cup 226, while the inner spring 262 urges the tip valve 251 downwardly relative to the washer 259. Also, positioned around the upper end of the tip valve and around the nut 261 is an annular impact button 264, the lower surface of the button 264 seating on the upper side of the washer 259. As shown in FIG. 10, the outer diameter of a step 265 of the button 264 is large enough to catch under the lower corner of the barrel 225 when the plunger 238 moves upwardly, thereby preventing the tip valve 251 from moving the entire distance upwardly with the plunger 238. Slots 266 (FIG. 10) are formed in the step 265 to permit fuel flow therethrough.

Considering the operation of the injector shown in FIGS. 10 to 12, assume that the plunger 238, which is driven by a cam as in the first described injector form, is in its uppermost position shown in FIG. 10. The spring 263 holds the washer 259 and the impact button 264 upwardly against the lower end of the barrel 225, and the tip valve 251 is in its uppermost position. It will be noted that the lower edge of the plunger 238 is above the metering orifice 232, and consequently, fuel is metered into the injection chamber 246 formed below the plunger. As previously mentioned, the amount of fuel metered into the injection chamber 246 varies with the pressure of the fuelsupply connected to the passage 228. The plunger 238 is forced downwardly by the cam actuating mechanism and the plunger closes the orifice 232 to end the metering portion of the injector cycle. When the plunger meets the fuel trapped in the chamber 246, the fuel is forced downwardly through the flow area formed by the flats 256 of the tip valve 251, to the sac hole 250, and out of the spray holes 254. I

Injection continues as the plunger 238 moves downwardly and the lower end of the plunger 238 strikes the upper end of the impact button 264. The spring 263 is compressed and the tip valve 251 is moved downwardly toward the seat 253. As in the form of the injector shown in FIGS. 1 to 7, when the portion 252 is sufficiently close tothe seat 253 that the flow area between the portion 252 and the seat 253 is less than the flow area of the holes 254, a hydraulic force develops on the tip valve 251, which abruptly moves the valve 251 downwardly away from the plunger 238 and against the seat 253. This position is shown in FIG. 11 and it is at this time that injection is terminated.

Essentially at the same time'as the termination of injection, the lower edge of the reduced diameter portion 241 of the plunger opens the spill port 242. As the plunger 238 continues to move downwardly, the hydraulic force on the tip valve holds the tip valve 251 firmly seated and thus prevents secondary emission, and continued downward movement of the plunger 238 causes the plunger to re-engage the impact button 264. The reduced diameter portion connects the ports 236 and 242 and permits a gradual release of the pressure within the metering chamber 246, the release being gradual because of the restricted orifice 248. When the plunger 238 is all the way down, as shown in FIG. 12, fuel flows from the supply passage 228, upwardly through the passage 231 and out of the scavenging port 233, across the upper reduced diameter portion 239 and to drain through the port 237. An overtravel gap 267 opens up between the nut 261 and the washer 259 at this time. The plunger 238 remains in the downward position until, during the suction stroke, the plunger rises. The tip valve, however, moves upwardly only to the position shown in FIG. 10, as previously mentioned.

Thus, the form of the injector shown in FIGS. to 12 is generally similar in construction and operation to the first described form of the injector, the two principal differences being, first, that the plunger 238 moves upwardly completely away from the tip valve 251, and secondly by the arrangement of the spill port.

A third form of the injector is shown in FIG. 13, which is similar in most respects to the form of the injector shown in FIGS. 10 through 12. It includes an injector barrel 271, a cup 272, a retainer 273 and an aligning ring 274 which may be provided to bridge the joint between the cup 272 and the barrel 271 in order to align these two parts. The fuel supply passages in the barrel 271 include a downwardly extending passage 276, an annular groove 277, an upwardly extending passage 278, a metering orifice 279, and a scavenging port 281, similar to the corresponding passages included in the injector of FIGS. 10 to 12. A drain port 282 is formed in the barrel 271 across the port 281 and a reduced diameter portion 283 of a plunger 284 connects the ports 281 and 282 when the plunger is downwardly displaced.

An injection chamber 286 is formed in the cup 272 and in the lower end of the barrel 271, below the plunger 284, and a tip valve 287 extends upwardly into the chamber 286. Two springs 288 and 289 and an impact button 291 are connected to the tip valve 287, similar to the corresponding components in the form of FIGS. 10 to 12. The outer diameter of the impact button 291 is sized to be held by a shoulder 292 of the barrel 271 and thus limit the upward movement of the impact button 291. A spill passage 293 connects the upper end of the injection chamber 286 with the plunger bore, and the spill port 294 of the passage 293 is located to be opened by the lower edge of the reduced diameter portion 283 of the plunger 284 at essentially the same time that the tip valve 287 terminates injection, similar to the other forms of the injector.

Whereas in the forms of the injector described in FIGS. 1 to 12 flow passages or grooves are formed in the sides of the tip valve, in the injector form shown in FIG. 13 a flow passage 296 is formed in the cup 272 to one side of the hole for the tip valve 287. The shank or central portion 297 of the tip valve 287 has a close sliding fit in a hole 298 formed in the cup 272. During injection of fuel, fuel flows from the upper end of the injection chamber 286, through holes 303 in the button 291, downwardly through the passage 296 to a cavity 299 formed in the cup 272 adjacent the lower end of the tip valve 287. The cavity 299 is just above a valve seat 305 for the tip valve 287. When the tip valve 287 is upwardly displaced, the cavity 299 is'in flow communication with a sac hole 301 and spray holes 302. The parts of the injector form of FIG. 13, which have not been described in detail, are generally similar to the corresponding parts of the earlier described forms.

Considering the operation of the injector shown in FIG. 13, assume that the plunger 284 and the tip valve 287 are upwardly displaced similar to the position of the injector parts shown in FIG. 10. Downward movement of the plunger 284 forces fuel downwardly through the holes 303 in the impact button 291, through the passage 296, the cavity 299 and out of spray holes 302.

Once again, the flow area of the passage 296 must be larger than the flow area of the spray holes 302 to prevent a hydraulic lock from occurring. When the plunger 284 moves downwardly, it strikes the impact button 291 and moves the tip valve 287 downwardly until the lower end surface 304 of the tip valve closely approaches the seat 305. As previously explained, the tip valve 287 is then abruptly moved downwardly by a hydraulic force to terminate injection. The remainder of the operation is generally similar to that of the injector form shown in FIGS. 10 to 12.

The form of the injector shown in FIG. 13 illustrates the fact that it is not necessary for fuel to flow through passages formed in or closely adjacent the tip valve for a hydraulic force to develop which seats the tip valve.

The form of the injector illustrated in FIGS. 14 and 15 is generally similar to that illustrated in FIGS. 10 to 12, the principal difference being that the pill port, when opened, spills the high pressure fuel from the injection chamber into a closed volume or space, rather than to a drain connection. The injector shown in FIGS. 14 and 15 includes a barrel] 310, a cup 311- and a retainer 312, these components being generally similar to the corresponding parts illustrated in FIGS. 10 to 12. A plunger 313 is reciprocablly mounted within a plunger bore 314 formed in the barrel 310, and a tip valve 316 is movably mounted within the cup 311 below the lower end of the plunger 313. A fuel supply passage (not shown) in the barrel 310 is connected to supply fuel to an annular passage 317 formed in the upper surface of the cup 311, and a vertically extending passage 318 is formed in the barrel 310 and extends upwardly from the passage 317. The passage 318 supplies fuel to a metering orifice 319 and to a scavenging port 321, both of which extend from the passage 318 to the plunger bore 314. A drain passage 322 isformed in the barrel 310 and includes a drain port 323 in the plunger bore 314 which is generally opposite the scavenging port 321.

The form of the injector shown in FIGS. 14 and 15 furthre includes an injection chamber 326 formed in the cup 311 and in the lower end of the barrel 310 below the plunger 313, the tip valve 316 extending into the injection chamber 326. Outer and inner springs 327 and 328 and an impact button 329 are positioned in the chamber 326 around the upper portion of the tip valve 316. Once again, the outer diameter of the'impact button 329 is large enough to catch under the lower corner of the barrel 310 to limit the extent of upward movement of the button 329 and the tip valve 316. As in the injector form shown in FIG. 13, the form shown in FIGS. 14 and 15 further includes a snap ring 331 fastened to the tip valve 316 and a washer 332 at approximately midway along its length, and a transversely enlarged head 333 is formed on the upper end of the tip valve 316. The impact button 329 is slidable on the tip valve 316 and hooks underneath the head 333. The inner spring 328 is positioned between the impact button 329 and the washer 332 while the outer spring 327 is positioned between the impact button 329 and a ledge 330 formed on the cup 311. The lower portion 334 of the tip valve 316 has flat sides 336 formed thereon, through which fuel flows during injection as previously explained in connection with an earlier described form. In the lower end of the cup 311 is formed a sac hole 337 and spray holes 338.

The barrel 310 further has a spill passage 341 formed therein extending from the upper end of injection chamber 326 to a spill port 342 opening to the plunger bore 314. The plunger 313 has a lower reduced diameter portion 343 formed therein which is located to open the spill port 342 as the plunger 313 approaches its maximum downwardly displaced position shown in FIG. 15. The drain port 323 is located so that it is opened by the reduced diameter portion 343 when the plunger 313 is upwardly displaced as shown in FIG. 14. Also, when the plunger 313 is downwardly displaced as shown in FIG. 15, the scavenging port 321 is placed in flow communication with'the drain port 323 by an upper reduced diameter portion 344 of the plunger 313. It should be noted from FIG. 15 that the reduced diameter portion 343 is not connected with the drain port 323 or any other fuel outlet passage when the portion 343 opens the spill port 342.

During operation of the form of the injector shown in FIGS. 14 and 15, when the plunger 313 and the tip valve 316 are in their upwardly displaced positions, shown in FIG. 14, the lower edge of the plunger 313 is above the metering orifice 319 and fuel flows from the supply passage 318 into the injection chamber 326. The land portion of the plunger 313, which is between the two reduced diameter portions 343 and 344, closes the scavenging port 321 and therefore no fuel flows out of this port. The lower reduced diameter portion 343 is in flow communication with the drain passage 322, and consequently the portion 343 is filled with fuel at drain, or atmospheric pressure. The spill port 342 is closed by the lower end portion of the plunger 313.

As the plunger 313 moves downwardly in an injection stroke, it closes the feed orifice 319, strikes the fuel in the injection chamber 326 and forces the fuel downwardly through holes formed in the impact button 329, through the passages 336 formed in the tip valve 316, into the sac hole 337 and out of the spray holes 338. Again, the flow area through the passages 336 must be greater than the flow area of the spray holes 338. The reduced diameter portion 343 remains filled with fuel at drain pressure during this downward movement of the plunger 313. Thelower end of the plunger 313 strikes the impact button 329 and moves it and the tip valve 316 downwardly until, as previously described, a hydraulic force develops on the tip valve 316 when the lower end of the tip valve 316 is close to the valve seat formed in the cup 311. The tip valve 316 is moved downwardly by hydraulic force and the impact button 329 moves downwardly away from the lower end of the plunger 313. The tip valve 316 quickly moves to its seated position to abruptly terminate injection and, substantially simultaneously, the lower edge of the reduced portion 343 opens the spill port 342. As the plunger 313 moves further downwardly, it again strikes the impact button 329, the spring 327 is.compressed and the plunger squeezes some of the fuel from the injection chamber 326 through the spill passage 341 and into the reduced diameter portion 343. The fuel in the portion 343 comes under extremely high pressure of the order of 25,000 psi, and at such pressures the fuel compresses slightly, thereby absorbing some of the force of the plunger 313 and the cam actuating mechanism. Such compression of the fuel plus any leakage of the fuel around the plunger to drain serves to gradually release the high pressure in the injection chamber 326. This pressure of course holds the tip valve 316 seated to prevent secondary injection.

When the plunger 313 subsequently moves upwardly again, it releases the pressure within the injection chamber 326 to permit the outer spring 327 to move the impact button 329 and the tip valve 316 upwardly once again to the position shown in FIG. 14. The high pressure fuel within the reduced diameter portion 343 is then vented to the drain passage 322 when the plunger 313 reaches the position shown in FIG. 14 at the start of the next operating cycle.

The form shown in FIGS. 14 and 15 is advantageous in that there is no tendency for air bubbles to form in the injection chamber as may be the case when the injection chamber is vented or spilled to a low pressure drain connection.

The form of the injector shown in FIG. 16 is generally similar to the form of the invention shown in FIGS. 10 to 12 but differs in the arrangement of the spill port and the spill passage. The injector of FIG. 16 includes a barrel 351, a cup or nozzle 352 and a retainer 353, similar to the above described forms. A fuel supply passage 354 formed in the barrel 351 carries fuel to a groove 355 in the cup 352 and to a vertically extending passage 356 in the barrel 351. A plunger bore 357 is formed in the barrel 351, and a metering orifice 358 and a scavenging port 359 are formed in the barrel 351 and connect the passage 356 with the plunger bore 357. A drain passage 361 formed in the barrel 351 has a drain port 362 generally opposite the scavenging port 359. A plunger 363 is reciprocably mounted in the bore 357 and includes a reduced diameter portion 364 which connects the scavenging port 359 with the drain port 362 when the plunger 363 is downwardly dis placed to the position shown in FIG. 16.

The injector further includes an injection chamber 366 formed in the cup 352 and in the barrel 351 below the plunger 363. A tip valve 367, outer and inner springs 368 and 369 and an impact button 371 are mounted around the tip valve 367 within the injection chamber 366 as previously explained in connection with other forms. Once again, the outer diameter of the impact button 371 is sufficiently large that it catches under the lower edge of the barrel 351 and thus limits the amount of upward movement of the impact button 371.

A shoulder or ledge 372 is also formed on the cup 352 within the injection chamber 366 and is sized to be engaged by the impact button 371 to limit its downward movement. The function is similar to that of the stop washer 129 (FIG. 2) which is engageable with the upper end of the adapter 101 to limit the downward movement of the plunger 127. The construction of the tip valve 367, the flow passages around it and the spray holes at the lower end of the cup 352 are similar to the corresponding parts of the injector form shown in FIGS. 14 and 15, and therefore are not described in detail.

Instead of providing a spill port and passage in the barrel 351 as in the above described forms of the invention, a spill passage 376 is formed in the plunger 363,

which extends from the reduced diameter portion 364 downwardly and diagonally of the plunger to a port 377 formed in one side and near the lower end of the plunger 363. The port 377 is located to be opened by being moved downwardly to the lower edge of the barrel 352, this occurring when the plunger 363 approaches its lowermost position, shown in FIG. 16. Once again, the pressure is released gradually when the drain port 377 opens because the size of the drain passage 376 is relatively small and because the drain port 377 is only slightly and gradually opened. Passages 370 may be formed through the impact button 371 to permit flow of fuel therethrough from the lower end of the injection chamber to the spill passage 376, when the button 371 has seated on the ledge 372. It will be noted that the flow of fuel from the scavenging port 359 to V the drain port 362 is through the reduced diameter portion 364 when the plunger 363 is downwardly displaced, and the fuel spilled through the spill passage 376 simultaneously flows through the reduced diameter portion 364 to the port 362. The. remainder of the construction and operation of the injector form shown in FIG. 16 is generally similar to the other described forms of the injector.

In the form of the injector shown in FIGS. 17 through 20, the tipvalve is movably connected to the plunger rather than being mounted separately from the plunger as in the previously described injector forms. Consequently, the tip valve of this form follows the line 193a (FIG. 8) rather than the line 193b as in the previously described forms. This injector form includes an adapter 385, a barrel 386, a cup 387 and a retainer 388 for holding the parts in assembled relation,.generally similar to the other forms. A fuel supply passage 389 is formed in the adapter 385, which supplies fuel to a supply passage 391 (FIG. 18) formed in the barrel 386, similar to the passages formed in the injector form shown in FIGS. 1 through 7. The lower end of the passage 391 connects with an annular groove 392 formed in the upper surface of the cup 387, and this groove 392 carries fuel to another vertically extending supply passage 393 (FIG. 18) formed in the barrel 386. The passage 393 is of course angularly displaced from the passage 391. A metering orifice 394 and a scavenging port 396 connect the passage 393 with a plunger bore 397 formed in the barrel 386 and in the adapter 385. With reference to FIGS. 17, 19 and 20, a drain passage 398 is formed in the barrel 386 and in the adapter 385, and connects the plunger bore 397 with'a drain groove 399 formed in the outer surface of the adapter 385.

The plunger bore 397 receives a reciprocable plunger 402 having .a reduced diameter portion 403 formed therein which is spaced upwardly from the lower end of the plunger. At the lower end of the plunger 402 is attached an upper hook-shaped part 404. The part 404 may be formed integrally with or separately from the plunger. The part 404 is connected to a similar hook-shaped part 407 on the upper end of a tip valve 406, the hook parts 404 and 407 being interconnected to form a lost motion connection. The part 407 may also be formed integrally with or separately .from the tip valve 406. A compression spring 408 is positioned around the two parts 404 and 407, and between the underside of the plunger 402 and the tip valve 406, and the compression spring 408 normally holds the tip valve 406 downwardly extended from the lower end of the plunger 402. A washer 409 and a snap ring 411 connect the spring 408 to the tip valve 406.

The tip valve 406 is slidably mounted in the hole 412 formed in the cup 387, and a valve portion 413 formed on the lower end of the tip valve 406 mates with a similarly shaped valve seat 414 formed in the cup 387 at the lower end of the hole 412. Once again, a sac hole 416 and spray holes 417 are formed in the lower end of the cup 387. A fuel flow passage is formed through the tip valve 406 by a longitudinally extending hole 419 formed in the central portion of the tip valve 406 and a transversely extending hole 421 formed in the tip valve near its lower end above the valve portion 413. The passage 419 extends from the transverse hole 421 upwardly through the hook-shaped portion 407, thus placing the upper portion of an injection chamber 422 in flow communication with the lower end of the hole 412.

A spill passage 423 and a spill port 424 are formed in the barrel 386 and connect the injection chamber 422 with the plunger bore 397 at a location where the spill port 424 is opened by the lower edge of the reduced diameter portion 403 when the plunger 402 approaches its maximum downwardly displaced position shown in FIG. 20.

Once again, the size of the passage 419 and the hole 421 must be greater than the size of the spray holes 417 to prevent a hydraulic lock from forming.

Considering the operation of the injector shown in FIGS. 17 to 20, assume that the injector plunger 402 and the tip valve 406 are initially in the upwardly displaced positions illustrated in FIGS. 17 and 18. In this position of the plunger, the scavenging port 396 (FIG. 18) and the port of the drain passage 398 (FIG. 17) are closed, and the metering orifice 394 is open. Fuel flows through the passages 389 and 391,. groove 392 and passage 393, and out of the orifice 394 into the injection chamber 422.

During downward movement of the plunger 402, fuel trapped in the injection chamber 422 flows downwardly through the passage 419 formed in the tip valve 406, out of the hole 421, downwardly to the sac hole 416 and out of the spray holes 417. The tip valve 406 is held extended downwardly in the position shown in FIGS. 17 and 18 by the compression spring 408 during this movement.

With reference to FIG. 19, the valve portion 413 of the tip valve 406 engages the valve seat 414 and terminates injection at substantially the same time that the spill port 424 is opened. When the valve portion 413 is close to the valve seat 414, a hydraulic force develops on the tip valve 406 as previously explained and this force holds the tip valve 406 extended from the plunger and prevents any possible compression of the spring 408 at this time. After the valve portion 413 has engaged the seat 414 and terminated injection, the hydraulic pressure within the injection chamber 422 holds the tip valve 406 seated to prevent secondary injection. The plunger 402 continues its downward movement after termination of injection to the maximum downwardly displaced position shown in FIG. 20, and the spring 408 compresses slightly while the two hook-shaped parts 404 and'407 move relative to each other to form an overtravel gap 430 (FIG. 20). The spill port 424 during this final movement is open and since the sizes of the spill passage 423 and the opening of the spill port are restricted, there is a gradual release in pressure in the injection chamber 422 as previously explained. I

When the plunger 402 is subsequently retracted, the hook-shaped part 404 again moves upwardly to engage the other hook-shaped part 407 and lift the tip valve 406 upwardly. The plunger and the tip valve are then returned to the position illustrated in FIGS. 17 and 18 by the retraction spring for the beginning of a new operating cycle.

The form of the injector illustrated in FIGS. 21 and 22 is similar to the form illustrated in FIGS. 17 through 20 in that the tip valve is attached by a lost motion connection to the lower end of the plunger. This form differs however in the construction and attachment of the tip valve with the plunger, and in the arrangement of the spill port. The injector form of FIGS. 21 and 22 includes a barrel 436, a cup 437, a retainer 438 and a plunger 439 The plunger 439 is reciprocably mounted in a plunger bore 441 formed in the barrel 436. A fuel supply passage 442 in the barrel 436 supplies fuel to an annular groove 443 in the cup 437, and a vertically extending passage 444 in the barrel 436 carries fuel to a metering orifice 446 and to a scavenging port 447. Also formed in the barrel 436 is a drain passage 448 connected to a drain port 449 and to a spill port 451, the ports 449 and 451 opening into the plunger bore 441.

An injection chamber452 is formed in the barrel 436 and in the cup 437 below the plunger 439, and a tip valve 453 is connected by a lost motion connection to the lower end of the plunger 439, the lost motion connection comprising an annular groove 454 formed in a reduced diameter section 455 of the lower end of the plunger 439 and inwardly extending ribs 456 formed on the upper end of the tip valve 453. The vertical dimension of the groove 454 is greater than the height of the ribs 456, and therefore the tip valve 453 is able to move vertically relative to the plunger 439. A compression spring 457 is positioned around the section 455, between the main body of the plunger and the tip valve 453, and urges the tip valve 453 downwardly from the plunger.

To fasten the tip valve 453 to the portion 455, a slot may be formed laterally through the .upper end of the tip valve, as by milling, and the portion 455 of the plunger may be inserted into the slot from one end thereof. Alternatively, a hole may be formed in the upper end of the tip valve and the edges of the hole deformed inwardly to form the ribs 456.

The tip valve 453 includes an upper cylindrical portion 460 and a conically shaped valve portion 461 which, upon downward'movement of the plunger and the tip valve, engages a complementary valve seat 462 formed in the cup 437. Below the valve seat 462 is formed a sac hole 463 and spray holes 464.

A spill passage 466 is formed in the lower end portion of the plunger 439, the lower end of the passage 466 being adjacent the upper end of the reduced diameter portion 455 and the upper end of the passage 466 opening into a reduced diameter portion 467 formed in the plunger 439. The portion 467 is located relative to the spill port 451 such that the lower edge of the portion 467 slightly opens the spill port 451 as the plunger 439 approaches its maximum downwardly displaced position, shown in FIG. 22. The plunger 439 also includes an. upper reduced diameter portion 468 which connects the drain and scavenging ports 449 and 447 when the plunger 339 is downwardly displaced as shown in FIG. 22. With reference to FIG. 21, it will be noted that the lower edge of the plunger 439 opens the metering orifice 446 when the plunger 439 is up.

When the plunger 439 is upwardly displaced as shown in FIG. 21, fuel flows from the metering orifice 446 into the injection chamber 452 and, as in the other forms of the injector, the amount of fuel flowing into the chamber 462 is a function of the pressure of the fuel supply. At the end of the fuel metering portion of the injector cycle, the plunger 439 is moved downwardly and the spring 457 holds the tip valve 453 extending downwardly from the plunger 439. After the plunger 439 has closed the metering orifice 446 and strikes the fuel in the chamber 452, the fuel is forced downwardly in the chamber 452 around the outer periphery of the cylindrical portion 460 of the tip valve 453, to the sac hole 463 and out of the spray holes 464. Once again, the size of the flow passage around the periphery of the cylindrical portion 460 must be greater than the size of spray holes 464. When the valve portion 461 of the tip valve 453 approaches the seat 462, a hydraulic force develops as previously explained and this hydraulic force holds the tip valve 453 extended from the plunger 439 and thus assures that the tip valve 453 will move rapidly onto the seat 462 in order to abruptly terminate injection. As the tip valve 453 is seated, the lower edge of the groove 467 opens the spill port 451. Pressure in the injection chamber 452 is gradually released as the plunger 439 completes its downward movement. After the plunger'439 has stopped at the position shown in FIG. 22, the pressure in the injec' tion chamber 452 continues to be gradually released, the gradual release being accomplished by the restricted size of the passage 466 and by the restricted opening of the spill port 451. As in the form of the injection of the injector shown in FIGS. 17 to 20, an overtravel gap 465 (FIG. 22) opens up at the connection between the tip valve 453 and the plunger 439. When the plunger 439 subsequently moves upwardly, it again engages the tip valve 453 and returns it to the position shown in FIG. 21.

The form of the injector illustrated in FIG. 23 is similar to that illustrated in FIGS. 21 and 22, the principal difference being that the fuel is spilled into a closed volume or chamber rather than to drain. Since most of the structure of the form shown in FIG. 23 is the same as that of the form of FIGS. 21 and 22, the details of construction will not be repeated. The form shown in FIG. 23 includes a spill port 470 formed in a barrel 471, the spill port 470 being connected to a chamber 472 formed in the barrel 471. The chamber 472 is of course similar to the passage 448 shown in FIGS. 21- and 22, but instead of being connected to drain, the upper end of the chamber 472 is closed by a plug or stop 473. The chamber 472 is filled with fuel during operation, and when the spill port 470 is opened upon downward movement of the plunger 474, fuel is spilled from the injection chamber into the chamber 472 rather than to the drain. This portion of the operation of the injector 423 is of course similar to that shown in FIG. 15 and therefore will not be described in further detail.

The form of the injector shown in FIG. 24 is also similar to the form shown in FIGS. 21 and 22 but differs in the manner in which thetip valve is connected to the lower end of the plunger. The arrangement shown in FIG. 24 may be advantageously used when the amount of space within the injector available for the injection chamber is limited. The form shown in FIG. 24 includes a plunger 481 which is reciprocably mounted in a plunger bore 482 formed in a barrel 483. A cup 484 is connected to the lower end of the barrel 483 by a retainer 486, and fuel flow passages are formed in the injector parts similar to the injector form illustrated in FIGS. 21 and 22.

A tip valve 487 is connected to the lower end of the plunger 481 by two semi-cylindrical sleeves 488 and 489 which, together, substantially encircle the lower end of the plunger 481" and the upper end of the tip valve 487. The upper and lower ends of the two halves 488 and 489 are both turned inwardly and engage annular grooves 491 and 492 formed in the lower end of the plunger 481 and in the upper end of the tip valve 487, respectively. The outer surfaces of the two halves 488 and 489 slidingly engage the inner wall of the cup 484 and thus are held in assembled relation with the plunger and the tip valve. A compression spring 493 is positioned between the plunger 481 and the tip valve 487 in order to hold the tip valve 487 extended downwardly from the plunger. The connection of the halves 488 and 489 with the plunger 481 and the tip valve 487 are lost motion connections and thus permit limited movement of the tip valve 487 relative to the plunger 381, as previously explained in connection with the form of the injector illustrated in FIGS. 21 and 22.

In summary, all of the form of the injector illustrated and described herein include novel means for abruptly terminating injection at the optimum time in the injector cycle, and also include novel means for preventing the occurrence of secondary injection. The hydraulic force developed on the tip valve, which is mounted for movement relative to the plunger in each of the injector forms, assures that the tip valve rapidly moves onto its valve seat in order to terminate injection. While all of the injector forms include a spill port, the spill port does not function to terminate injection but, rather, to relieve pressure within the injection chamber, while the tip valve performs the function of terminating injection. Because of this operation, the injector is able to maintain pressure on the tip valve in order to prevent secondary injection. Further, the flow of fuel from the injection chamber through the spill passage is restricted, thus providing a gradual release in pressure in the injection chamber.

1 claim:

1. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a plunger bore formed therein, a reciprocable plunger mounted in said bore, said body further having an injection chamber and spray holes therein, said spray holes connecting said chamber with said engine cylinder, a r115 valve having a valve portion thereon, said body having a valve seat mating with said valve portion and located in the path of fuel flow from said chamber to said spray holes, means normally holding said tip valveoffsaid yalye seat but sarenavivb aiigmvaiowam said seat by movement of said plunger to seat said valve portion on said valve seat, and pressure release means connected to said chamber'and actuated by movement of said plunger to release pressure in said injection chamber at the same time or after the time that said valve portion seats on said valve seat.

2. An injector as in claim 1, wherein said pressure release means comprises a spill passage leading from said injection chamber, said passage having a restricted flow area to effect a gradual release in pressure in said injection chamber.

3. An injector as in claim 1, wherein said path of fuel flow from said chamber to said spray holes is through a passage between said valve portion and said seat, the flow area of said passage decreasing as said tip valve is moved toward said seat by said movement of said plunger, and wherein a hydraulic force develops on said tip valve when the flow area of said spray holes becomes greater than said flow area between said valve portion and said seat, said hydraulic force tending to move said tip valve toward said seat and causing an abrupt termination of injection.

4. A fuel injector as in claim 1, wherein said tip valve is movably mounted in said body separate from said plunger, said plunger moving into engagement with said tip valve to move said tip valve toward said seat.

5. A fuel injector as in claim 1, wherein said tip valve is movably mounted in said body and is connected to said plunger by a lost motion connection.

6. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising a plunger body having an injection chamber, plunger means for forcing fuel out of said chamber and into an engine cylinder, valve means in the flow path of fuel flowing out of said chamber for terminating injection, and pressure release means in said body for releasing pressure in said chamber at the same time or after the time that said valve means terminates injection.

7. A fuel injector as in claim 6, wherein said pressure release means gradually releases pressure in said chamber.

8. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a fuel flow passage formed therein, means for forcing fuel under pressure through said passage, said body further having spray holes formed therein for the flow of fuel through said passage and into said cylinder, valve means in said passage including a valve seat formed in said body and a movable valve member, said valve member blocking the flow of fuel through said passage to said spray holes when said member engages said valve seat and permitting such flow when said member is displaced from said'seat, means for normally holding said valve member away from said valve seat, means for moving said valve member toward said seat during an injection stroke, the flow area through said spray holes being greater than the flow area between said member and said seat when said member is displaced, and said flow area between said member and said seat becoming less than said flow area through said spray holes when said member closely approaches said seat, whereby the fuel flow through said valve means is throttled causing the pressure upstream of said valve means to become greater than the pressure downstream of said valve means, said greater pressure tending to move said member to'and holding said member on said seat.

9. A fuel injector as in claim 8, wherein a portion of said passage is upstream of said valve seat and is formed in said valve member.

10. A fuel injector as in claim 8, wherein a portion of said passage is upstream of said valve seat and is.

formed in said body to one side of said valve member. 

1. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a plunger bore formed therein, a reciprocable plunger mounted in said bore, said body further having an injection chamber and spray holes therein, said spray holes connecting said chamber with said engine cylinder, a tip valve having a vale portion thereon, said body having a valve seat mating with said valve portion and located in the path of fuel flow from said chamber to said spray holes, means normally holding said tip valve off said valve seat but said tip valve being moved toward said seat by movement of said plunger to seat said valve portion on said valve seat, and pressure release means connected to said chamber and actuated by movement of said plunger to release pressure in said injection chamber at the same time or after the time that said valve portion seats on said valve seat.
 2. An injector as in claim 1, wherein said pressure release means comprises a spill passage leading from said injection chamber, said passage having a restricted flow area to effect a gradual release in pressure in said injection chamber.
 3. An injector as in claim 1, wherein said path of fuel flow from said chamber to said spray holes is through a passage between said valve portion and said seat, the flow area of said passage decreasing as said tip valve is moved toward said seat by said movement of said plunger, and wherein a hydraulic force develops on said tip valve when the flow area of said spray holes becomes greater than said flow area betweeN said valve portion and said seat, said hydraulic force tending to move said tip valve toward said seat and causing an abrupt termination of injection.
 4. A fuel injector as in claim 1, wherein said tip valve is movably mounted in said body separate from said plunger, said plunger moving into engagement with said tip valve to move said tip valve toward said seat.
 5. A fuel injector as in claim 1, wherein said tip valve is movably mounted in said body and is connected to said plunger by a lost motion connection.
 6. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising a plunger body having an injection chamber, plunger means for forcing fuel out of said chamber and into an engine cylinder, valve means in the flow path of fuel flowing out of said chamber for terminating injection, and pressure release means in said body for releasing pressure in said chamber at the same time or after the time that said valve means terminates injection.
 7. A fuel injector as in claim 6, wherein said pressure release means gradually releases pressure in said chamber.
 8. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a fuel flow passage formed therein, means for forcing fuel under pressure through said passage, said body further having spray holes formed therein for the flow of fuel through said passage and into said cylinder, valve means in said passage including a valve seat formed in said body and a movable valve member, said valve member blocking the flow of fuel through said passage to said spray holes when said member engages said valve seat and permitting such flow when said member is displaced from said seat, means for normally holding said valve member away from said valve seat, means for moving said valve member toward said seat during an injection stroke, the flow area through said spray holes being greater than the flow area between said member and said seat when said member is displaced, and said flow area between said member and said seat becoming less than said flow area through said spray holes when said member closely approaches said seat, whereby the fuel flow through said valve means is throttled causing the pressure upstream of said valve means to become greater than the pressure downstream of said valve means, said greater pressure tending to move said member to and holding said member on said seat.
 9. A fuel injector as in claim 8, wherein a portion of said passage is upstream of said valve seat and is formed in said valve member.
 10. A fuel injector as in claim 8, wherein a portion of said passage is upstream of said valve seat and is formed in said body to one side of said valve member.
 11. A fuel injector as in claim 8, and further including means in said injector body for releasing pressure in said passage upstream of said seat essentially at the same time that said member engages said seat.
 12. A fuel injector as in claim 11, wherein said pressure release means gradually releases said pressure, whereby said pressure is sufficiently maintained to hold said valve member seated and prevent secondary injection.
 13. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a chamber formed therein adapted to be connected to receive fuel from a fuel supply, said body further having spray holes formed therein and fuel passage means connecting said chamber with said spray holes, valve means in said passage for closing said passage to terminate the flow of fuel from said chamber to said spray holes, a plunger reciprocably mounted in said body and forcing fuel out of said chamber through said passage when moved in an injection stroke, and restricted flow spill passage means leading from said chamber and being the only outlet for fuel from said chamber when said valve means is closed at the end of said injection stroke, whereby the fuel contained in said chamber cushions and sTops the movement of said plunger without mechanical impact of said plunger on said body.
 14. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having an injection chamber formed thereon, said body further having formed therein spray holes, a passage connecting said chamber with said spray holes, valve means in said passage including a seat formed in said body and a valve member movable between an open position where it opens said passage and a seated position where it closes said passage, a plunger mounted in said body and movable in an injection stroke to force fuel from said chamber through said passage when said member is in said open position and out of said spray holes, said plunger moving said valve member from said open position toward said seated position during said injection stroke, said valve member being moved to said seated position and terminating injection before said plunger reaches the end of said injection stroke, and means for starting release of pressure in said chamber between the time said valve member reaches said seated position and the time said plunger reaches the end of said injection stroke.
 15. A fuel injector as in claim 14, wherein said pressure release means comprises a spill passage connected to said chamber, and said plunger opening said passage at essentially the same time that said valve member reaches said seated position.
 16. A fuel injector as in claim 15, wherein said spill passage leads to a low pressure drain connection.
 17. A fuel injector as in claim 15, wherein said spill passage leads to a closed chamber.
 18. A fuel injector as in claim 17, wherein said closed chamber is formed in said plunger.
 19. A fuel injector as in claim 17, wherein said closed chamber is formed in said injector body.
 20. A fuel injector as in claim 17, wherein said plunger connects said closed chamber to a drain while said spill passage is closed.
 21. A fuel injector as in claim 15, wherein said spill passage is formed in said body.
 22. A fuel injector as in claim 15, wherein said spill passage is formed in said plunger.
 23. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a plunger bore formed therein, a reciprocable plunger mounted in said bore, said body further having an injection chamber and spray holes therein and a passage connecting said chamber with said holes, said spray holes being adapted to connect said chamber with said cylinder, a tip valve having a valve portion thereon, said body having a valve seat in said passage adapted to mate with said valve portion, spring means between said tip valve and said body for urging said tip valve away from said seat and toward said plunger, said plunger engaging said tip valve and moving said tip valve toward said seat until the flow area between said valve portion and said valve seat becomes less than the flow area of said spray holes at which time a hydraulic force develops on said tip valve forcing said tip valve out of engagement with said plunger and onto said valve seat.
 24. A fuel injector as in claim 23, wherein said plunger re-engages said tip valve after said tip valve has been moved onto said seat.
 25. A fuel injector as in claim 24 and further including means between said plunger and said tip valve permitting said plunger to continue moving relative to said tip valve after reengaging said tip valve.
 26. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having formed therein a plunger bore, an injection chamber, spray holes and a passage connecting said chamber with said spray holes, a plunger reciprocably mounted in said bore and forcing fuel from said injection chamber and through said passage when moved in an injection stroke, a tip valve movably mounted in said chamber and having a valve portion extending into said passage, a valve seat formed in said passage And mating with said valve portion, first spring means connecting said body with said tip valve and urging said tip valve away from said seat and toward said plunger, second spring mean connected to said tip valve and engaged by said plunger during at least a portion of said injection stroke, whereby said first spring holds said tip valve away from said seat prior to said injection stroke, and said plunger acts through said second spring means to move said tip valve toward said seat during said injection stroke.
 27. A fuel injector as in claim 26, wherein said first spring means moves said tip valve and said second spring means and holds said second spring means engaged with said plunger prior to the start of said injection stroke.
 28. A fuel injector as in claim 27, and further including means on said body for limiting the extent of movement of said tip valve due to the force of said first spring means.
 29. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having formed therein a plunger bore, an injection chamber, spray holes and a passage connecting said chamber with said spray holes, a plunger reciprocably mounted in said bore and forcing fuel from said injection chamber and through said passage when moved in an injection stroke, a tip valve movably mounted in said chamber and having a valve portion extending into said passage, a valve seat formed in said passage and mating with said valve portion, a lost motion connection between said plunger and said tip valve, spring means connected to said tip valve and urging said tip valve toward said seat and away from said plunger, and spill means connected to said chamber for relieving pressure in said chamber at the same time as or after said valve portion engages said seat and terminates injection.
 30. A fuel injector as in claim 29, wherein said lost motion connection comprises hook portions on said plunger and on said tip valve.
 31. A fuel injector as in claim 30, wherein said hook portions comprise two semi-cylindrical sleeves which encircle and engage adjacent portions of said plunger and said tip valve.
 32. A fuel injector for injecting fuel into a cylinder of an internal combustion engine, comprising an injector body having a plunger bore formed therein, a reciprocable plunger mounted in said bore, said body further having an injection chamber and spray holes therein, said spray holes being adapted to connect said chamber with said cylinder, a tip valve movably mounted in said body and having a valve portion at one end thereof, said body having a valve seat adapted to mate with said valve portion and located in the path of fuel flow from said chamber to said spray holes, said plunger being adapted to be moved in an injection stroke to exert pressure on fuel in said injection chamber and the other end of said tip valve being exposed to said pressure of the fuel in said injection chamber, said tip valve being moved toward said seat by said movement of said plunger to seat said valve portion on said valve seat, and said pressure of the fuel in said injection chamber on said other end forcing said tip valve toward said seat and holding said tip valve on said seat after seating.
 33. A fuel injector as in claim 32, and further including means connected to said injection chamber for gradually releasing said pressure after said seating.
 34. A fuel injector as in claim 33, wherein said pressure release means comprises a spill port connected to said injection chamber.
 35. A fuel injector as in claim 32, wherein said tip valve is mounted in said body separating from said plunger, and said pressure in said injection chamber both moves said tip valve onto and holds said tip valve on said seat. 